A construction technology of main structure of a small-curvature teardrop-shaped cable tower

Abstract

The invention discloses a construction process of a main structure of a small-curvature teardrop-shaped cable tower, which is characterized by comprising the following steps: step 1: tower base construction; step 2: connection plate construction; step 3: tower column construction; step 4: lower cross beam construction; wherein step 2 includes steel anchor beam construction, steel anchor beam and corbel integral hoisting, and the installation of the embedded cable guide tube is carried out after the steel anchor beam system is installed and positioned, at which time the connecting bolts between the steel anchor beam and the steel corbel do not need to be tightened in place, and a gap is left for adjustment. If the accuracy requirement is not met, the position of the lower port is fine-tuned to the deviation meeting the accuracy requirement under the premise of meeting the smoothness requirement, and after the steel anchor beam is positioned, a longitudinal limit device of the steel anchor beam is installed, the limit device is perpendicular to the center line of the bridge tower, and the limit device is connected and fixed by a pre-embedded steel plate pre-embedded in the tower wall. The invention ensures the construction efficiency and assembly accuracy of the steel anchor beam and steel corbel unit assembly construction, and enables the main tower to have good technical guarantee.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a construction process for a main structure of a teardrop-shaped cable tower with a small curvature. Background Art

[0002] A bridge is a composite structure consisting of cables, towers, and beams as basic structures, among which beams and towers are the main load-bearing components, and the two are combined into an overall structure. The cable tower of a cable-stayed bridge is a tower-shaped structure that supports the main cable, which is usually a concrete tower.

[0003] In the prior art, the conventional construction process of cable-stayed bridge towers is usually to cast the foundation once or twice, and the tower column is constructed using hydraulic climbing formwork. The construction of the tower column is an aerial operation. The main tower structure of the teardrop-shaped tower is composed of curved structures on both sides. In this case, if the existing climbing formwork system uses the traditional method of replacing the curve with a straight line to cast the main tower, it is difficult to ensure that the main tower appearance is straight, and there is a large error.

[0004] The cable-stayed cable anchoring device in the main tower of the cable-stayed bridge adopts the structural design of steel anchor beams and steel bracket units. The installation accuracy directly affects the installation accuracy of the cable and the final control of the cable force of the bridge. Therefore, the accuracy control of the steel anchor beams and steel bracket units in the anchoring device of the main tower of the cable-stayed bridge is the key to the construction of the main tower. Since both sides of the small curvature teardrop-shaped cable tower are curved, the cable-stayed cable anchoring device therein also needs to be arranged in a curved shape when it is set. In this way, how to ensure the construction efficiency and assembly accuracy of the steel anchor beam and steel bracket unit assembly construction, and make the main tower have good technical security has become a technical problem that the existing technology needs to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a construction process for the main structure of a small-curvature teardrop-shaped cable tower, which is used to solve the technical problem in the prior art that it is difficult to ensure the construction efficiency and assembly accuracy of the assembly construction of steel anchor beams and steel corbel units in a small-curvature teardrop-shaped cable tower with a curved structure.

[0006] The construction process of the main structure of a small-curvature teardrop-shaped cable tower comprises the following steps:

[0007] Step 1: Tower base construction;

[0008] Step 2: Connection plate construction;

[0009] Step 3: Tower column construction;

[0010] Step 4: Construction of lower beam;

[0011] Step 5: Construction of upper beam;

[0012] Wherein step 2 comprises the construction of steel anchor beam, the integral hoisting of steel anchor beam and corbel, connecting the steel corbel into a whole by means of temporary connecting braces arranged at the upper and lower ends of the wall panel, after hoisting into place, re-measure the design positions of the anchor beam and corbel, and complete the installation of the steel anchor beam system, and the installation of the embedded cable guide tube is carried out after the steel anchor beam system is installed and positioned, at this time, the connecting bolts between the steel anchor beam and the steel corbel do not need to be tightened in place, and a gap is left for adjustment, if the accuracy requirement is not met, the position of the lower port is fine-tuned until the deviation meets the accuracy requirement under the premise of meeting the smoothness requirement, after the steel anchor beam is positioned, the longitudinal limit device of the steel anchor beam is installed, the limit device is perpendicular to the center line of the bridge tower, the limit device is connected and fixed by means of an embedded steel plate embedded in the tower wall in advance, one end is welded to the upper end of the steel anchor beam, the end of the limit device is melted through the steel anchor beam, and the other end is fixed on the embedded steel plate.

[0013] Preferably, the steps of constructing the steel anchor beam include:

[0014] Step 1: Install the rigid frame on the poured concrete;

[0015] Step 2: Use the tower crane to hoist the steel anchor beam and steel bracket as a whole; hoist the steel anchor beam onto the rigid frame, use the steel anchor beam on the bottom layer for positioning, and use the jack and hand winch for precise adjustment; after the installation accuracy meets the specification requirements, connect and reinforce the steel bracket and the rigid frame;

[0016] Step 3: Tie up the steel bars, install the formwork and pour the concrete; after the concrete pouring is completed, remove the connecting bolts between the steel bracket and the steel anchor beam at one end to make it free; repeat steps 1 to 3 to install the remaining steel anchor beams.

[0017] Preferably, the construction of the first section of steel anchor beam includes the installation of support frame, reinforcement of steel anchor beam corbel wall panel, and installation of cable guide tube and limit device; before the installation of the first section of steel anchor beam, a layer of connecting brace is set on the top of the corbel; the connecting brace and the corbel are connected by bolts; the steel anchor beam system is hoisted by a special hanger to eliminate the internal force and deformation of the corbel wall panel.

[0018] Preferably, the installation and erection of the support frame includes: pre-embedding the foundation embedded parts of the installation support steel bracket of the first section of the steel anchor beam on the top surface of the inner cavity of the upper tower column, and then installing and erecting the support bracket; the bottom of the bracket is supported on the foundation embedded parts, and after the installation is completed, the top surface is ensured to be flat, and the flatness is controlled within 5mm. Before the steel anchor beam is dropped, the elevation of the top of the bracket is re-measured, and according to the elevation of the bottom of the first section of the steel anchor beam to be installed, the bracket is padded, and the elevation is controlled by adding or reducing thin steel plates. If there is a deviation in the plane position when the steel anchor beam is dropped on the bracket, the plane position needs to be calibrated by a jack. After the plane position verification is completed, the elevation is calibrated by a thin steel plate prepared in advance. When the absolute elevation of the steel anchor beam meets the requirements, the steel anchor beam is temporarily fixed; in order to avoid the relative height difference of the four corners of the steel anchor beam wall panel exceeding the limit and affecting the subsequent steel anchor beam installation accuracy, it is necessary to observe the measurement results for two consecutive days and nights. When the final data is stable and meets the design requirements, the steel bracket wall panel is welded and fixed to the pre-installed rigid frame to complete the precise positioning of the first section of the steel anchor beam system.

[0019] Preferably, the cable guide tube is temporarily connected to the steel anchor beam and then hoisted together to control the installation axis to fit with the theoretical axis; the cable guide tube positioning bracket is welded and set on the rigid frame that has been installed in advance along the coordinate control points of the upper and lower ports of the cable guide tube, and a positioning bracket is welded at each end of the cable guide tube, and another positioning bracket is added every 1m in the middle of the cable guide tube; the pre-buried cable guide tube is installed after the steel anchor beam system is installed and positioned.

[0020] Preferably, after the first section of the steel anchor beam is installed, the standard section steel anchor beam system is installed in the following steps. The construction of the standard section steel anchor beam includes: the bracket is hoisted together with the anchor beam, and a docking bracket device is set on the wall plate of the steel anchor beam bracket against the inner cavity side of the tower column, with two upper and lower wall plates set on each side. The subsequent height connection installation is based on the docking bracket welded on the wall plate of the steel bracket installed last time for docking connection; first install the two temporarily connected steel anchor beam brackets, and when the height and position of the height connection steel bracket and the wall plate docking bracket of the steel bracket installed last time are basically aligned, slowly release the tower Lift the big hook until the weight of the steel corbel to be installed is all borne by the wall panel with the installed steel corbel. During this period, the position of the connecting corbel should be slightly adjusted to achieve the purpose of installing the connecting pins first and then the connecting bolts. At the same time, remeasure the top plane position, elevation and relative height difference of the four corners of the connected steel corbel. After all are qualified, position the steel anchor beam; remeasure the top plane position, elevation and relative height difference of the four corners of the installed steel anchor beam. After all are qualified, tighten the corbel connecting bolts to complete the connection installation of the standard segment steel anchor beam system; then proceed to the reinforced formwork concrete construction of the tower column of this segment.

[0021] Preferably, step 3 also includes: the rigid frame is processed in sections and frames, hoisted on site, and connected into a whole with steel sections, the rigid frame includes column trusses, horizontal cross bars, horizontal truss outer frames and diagonal bars, the vertical main reinforcement of the tower column is tied in sections, and the connection process is a rolled straight thread joint, and the stirrups and horizontal steel bars are connected by binding joints or lap welding.

[0022] Preferably, in step 3, the tower column is constructed by hydraulic climbing formwork, and both the inner and outer formworks are made of wooden beam glued formworks, including a panel, a shaping wood, a wooden back rib and a steel main beam. The inner and outer formworks are adjusted in line shape by inserting a shaping wood between the panel and the wooden beam in the vertical curved section of the tower column. The shaping wood is made of wooden strips, processed according to the line shape of the tower column, and fixed to the panel and the wooden beam by wooden nails; the panel and the wooden back rib are connected by wood screws, and the wooden back rib is connected to the steel main beam by connecting claws, and tie rods are used between the inner and outer formworks to overcome the lateral pressure of the concrete.

[0023] The present invention has the following advantages: before the steel anchor beam and the steel corbel are fully tightened, the present solution can fine-tune the position of the lower port so that the position deviation with the lower port of the steel sleeve meets the requirements and meets the accuracy requirements. Since the plane where the curve is located is the plane where the center line of the bridge tower is located, the distance from the tower wall to the steel anchor beam on the limiting structure in the direction perpendicular to the center line of the bridge tower, i.e. the longitudinal direction, is not affected by the curved structure of the bridge tower. Therefore, the cable guide tube and the steel anchor beam can be accurately positioned and fixed by the limiting structure after fine-tuning. Combined with the standard steel anchor beam system installation method, it can overcome the technical problem of the difficulty in ensuring the construction efficiency and assembly accuracy of the steel anchor beam and steel corbel unit assembly construction in the small curvature teardrop-shaped cable tower with curved structure in the prior art, and ensure the reliable installation efficiency and accuracy of the steel anchor beam system installation.

[0024] At the same time, the temporary fixing method and gap retention effect between the steel anchor beam and the steel bracket during construction make it possible to fine-tune the position of the steel anchor beam during construction. The installation and positioning method of the support frame can ensure that the installation accuracy of the first section of the steel anchor beam meets the requirements, and through a period of observation and measurement, it is avoided that the relative height difference of the four corners of the steel anchor beam wall plate exceeds the limit and affects the subsequent installation accuracy of the steel anchor beam. The introduction of shaped wood instead of the traditional method of replacing curves with straight lines in the construction of the main tower of the bridge tower can ensure that the main tower has a straight appearance line shape, and it is easy to adjust the template line shape to prevent the template from being overstressed locally. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flowchart of a construction process for a main structure of a small-curvature teardrop-shaped cable tower.

[0026] Figure 2 This is a vertical layout diagram of the steel anchor beam of the present invention.

[0027] Figure 3 , 4It is a schematic diagram of the arrangement of the support bracket of the present invention.

[0028] Figure 5 , 6 It is a schematic structural diagram of the limiting device of the present invention.

[0029] Figure 7 It is a schematic structural diagram of the template using the molding wood in the present invention in application.

[0030] Figure 8 It is a schematic diagram of the template arrangement of the tower column part in the present invention. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention will be further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0032] like Figure 1-8 As shown, the present invention provides a construction process for a main structure of a small-curvature teardrop-shaped cable tower, comprising the following steps.

[0033] It includes the following construction steps:

[0034] Step 1: Tower base construction.

[0035] The tower base is rectangular, 2.0m high, with a plane size of 15m (transverse direction) x 15m (longitudinal direction). The tower base is made of C50 concrete, and the concrete volume of a single tower base is 427.5m 3 The bottom 1m of the lower tower column and the tower base are poured at one time. This step includes the tower base reinforcement construction, tower base formwork construction and tower base concrete construction.

[0036] Tower base reinforcement construction: Tower base reinforcement is divided into two specifications, with diameters of C25 and C20 epoxy reinforcement. Except for the erection reinforcement, which is C25 epoxy reinforcement, the rest of the reinforcement is C20 epoxy reinforcement. Rebar processing flow: batch design → straightening, rust removal → cutting → bending → welding → inspection → inventory marking.

[0037] Tower base template construction: The tower base template uses a standard steel template. Before installing the tower base template, its surface should be polished and cleaned to ensure that there is no dirt or rust on the surface, and then a release agent should be applied. Measure and lay out the corner points of the tower base edge line, set up the template with a line, and install the template with a crawler crane and manual labor.

[0038] Tower base concrete construction: The tower base uses C50 concrete, and anti-cracking fiber is added to the concrete. The amount of anti-cracking fiber is determined by experiments. The concrete is produced by a mixing station 120 station, and the conveyor truck is transported to the site through the access road and the trestle. The concrete is poured by a pump truck. One pouring point is arranged on the side of the pier, and the pouring point is arranged in parallel. The concrete is poured from one end of the tower base to the other end. The overall pouring method is layered pouring and inclined advancement. The layer thickness is strictly controlled. The pouring thickness of each layer is controlled according to 30cm. When the concrete is poured in layers, the initial setting time of the upper and lower layers should not exceed that of the concrete.

[0039] Step 2: Connecting plate construction.

[0040] The tower column connection plate is located at the bottom of the tower column, connecting the two limbs of the tower column, and contains a water hole in the middle. This step includes steel bar construction, formwork construction and concrete construction.

[0041] Reinforcement construction: The connecting plate reinforcements are all made of ordinary HRB400 reinforcements. The connecting plate is constructed three times simultaneously with the 1st to 3rd sections of the tower column. The connecting plate reinforcements are tied synchronously when the tower base and tower column reinforcements are tied. The horizontal reinforcements of the connecting plate are inserted into the tower base and tower column, and the vertical reinforcements are inserted into the pedestal 1m except for the water hole section. The vertical main reinforcement is embedded during the construction of the pedestal, and the subsequent vertical reinforcements are connected to the reserved sleeves. A 3m post-casting strip is set in the middle of the connecting plate, and the horizontal reinforcement is not broken at the post-casting strip and is arranged throughout the length.

[0042] Formwork construction: The side formwork of the connection plate is installed using the 3m×2m steel formwork of the pedestal. The formwork at the post-casting strip uses a wooden formwork as the end formwork. Since the transverse steel bars are arranged throughout the length, the area around the steel bars needs to be blocked during the installation of the end formwork to prevent large-scale leakage of concrete. The side of the connection plate close to the tower column cannot be directly installed using a steel formwork due to the influence of the tower column line shape. Therefore, the side formwork close to the tower column is connected to the tower column formwork using a wooden formwork, and the vertical and horizontal back ribs of the wooden formwork are steel pipes and wooden squares. Double-sided tape is used to block the connection between wooden formworks, and foam glue is used to block the wooden formwork and steel formwork.

[0043] Concrete construction: C50 concrete is used for the connection plate. The concrete is transported to the site by a conveyor truck through the access road and the trestle, and poured by a pump truck. The connection plate is poured in three times, and is constructed and poured simultaneously with the first, second and third sections of the tower column.

[0044] Step 3: Tower column construction.

[0045] This step includes reinforcement construction, formwork construction and concrete construction.

[0046] Rebar construction: Epoxy resin coated steel bars are used for tower columns below +12.0m in elevation. Rebar construction includes rigid skeleton design and construction, and steel bar installation.

[0047] Rigid frame design and construction: The main bridge adopts a teardrop-shaped bridge tower structure. In order to accurately locate the tower column steel bars and speed up the construction progress, a rigid frame is set on the tower column. The rigid frame is processed in sections and segments, hoisted on site, and connected into a whole with steel sections.

[0048] According to the tower column segment height and the cantilever length of the main reinforcement, the standard segment length of the rigid frame is determined to be 6m, and the length of the rigid frame of special parts can be adjusted. The rigid frame is mainly made and connected by steel. In order to facilitate transportation and on-site positioning and installation, the rigid frame is composed of small-section trusses and connectors.

[0049] The rigid frame is composed of column trusses, horizontal cross bars and diagonal bars. The columns are made of ∠100×10mm angle steel, and the horizontal truss outer frame, large diagonal bars and small diagonal bars in the truss are made of ∠75×8mm angle steel.

[0050] Rigid frame construction: After the rigid frame is processed, it is transported to the site for on-site installation.

[0051] First, the skeleton is embedded during the construction of the pedestal and tower base, and the embedded part extends 20cm out of the top surface of the concrete pouring section. The starting section of the lower tower column is hoisted by a crawler crane. After the tower crane is installed, the truss is hoisted by a tower crane. The construction personnel hang a plumb line to check whether its tilt position meets the requirements. When the requirements are met, the skeleton and the connecting plate are welded immediately.

[0052] The tower column truss is hoisted and welded as a whole. The installation order of the small-section truss is the middle first and then the two sides. After the small-section truss is installed, the horizontal positioning angle steel is welded on the small-section truss. Points are placed on the positioning angle steel and the small-section truss to determine the position lines of the main reinforcement on both sides, and then the horizontal flat joints are installed and welded according to the position lines.

[0053] Rigid skeleton construction: The vertical main reinforcement of the tower column is connected by segmented binding and rolled straight thread joints. The standard segment length of the vertical main reinforcement of the tower column is 6.0m. The tower column steel bars are cut in the steel bar processing yard, the joints are rolled, and the straight thread heads are processed. After the thread heads are covered with plastic protective covers, they are bundled and transported to the construction site for use. The stirrups and horizontal steel bars are connected by binding joints or lap welding.

[0054] Formwork construction: The tower column is constructed with hydraulic climbing formwork, and both the internal and external formworks are made of wooden beam glued formwork, and the panel is made of 21mm plywood. The pouring height of the standard section of the tower column is 6.0m, and the formwork system used is also a corresponding symmetrical structure. The design height of the large-area formwork is 6.15m, of which the lower 0.10m is used as a pressure foot for the new and old concrete surfaces, and the upper 0.05m prevents the concrete slurry from overflowing and polluting the concrete surface and working platform.

[0055] Except for the 1st and 2nd sections of the lower tower column, the remaining sections are divided into 25 sections (including the top of the tower), with a standard section of 6.0m, all of which are constructed using the climbing formwork method. The inner and outer formworks in the formwork composition are both wooden beam glued formworks, mainly composed of panels, shaped wood, wooden back ribs, steel main beams, etc. The wooden back ribs are 20cm wooden I-beams, the steel main beams are 14# double-channel steel, and the panels are 21mm plywood.

[0056] The design height of the large-area formwork is 6.15m, of which the lower part of about 0.10m is used as the pressure foot of the new and old concrete surfaces, and the upper part of about 0.05m prevents the concrete slurry from overflowing and polluting the outer surface of the concrete. The internal and external formwork is adjusted by inserting a molding wood between the panel and the wooden beam in the vertical curve section of the tower column. The molding wood is made of wooden strips, processed according to the line shape of the tower column, and fixed to the panel and wooden beam by wooden nails. This method replaces the traditional construction method of replacing the curve with the straight one, which is more in line with the design curve of the tower column.

[0057] The panel is connected to the wooden back rib by wood screws, and the wooden back rib is connected to the steel main beam by connecting claws. The three are organically consolidated into a whole. Tie rods are used between the inner and outer templates to overcome the lateral pressure of the concrete. The tie rods use φ20 screws. Two hanging points are symmetrically set on each large-area template to facilitate the lifting of the lifting equipment and the position adjustment during the demoulding process. When the entire climbing structure is fully installed, it can automatically rise and fall using its own hydraulic transmission equipment without the need for external machinery.

[0058] Concrete construction: The main tower concrete uses C50 concrete, and the tower column concrete is produced by a mixing station and distributed to the pouring position by a drag pump through a pump pipe and a concrete distributor. The spacing of the string tubes is 3.0m, and the length of a single string tube is 1.0m. According to the pouring height, the length of the string tube is extended or shortened during the pouring process to ensure that the free fall height of the concrete is not more than 2.0m. The tower column concrete adopts the construction method of layered pouring, symmetrical layered distribution, and layered vibration. The thickness of each layer is 30cm.

[0059] Construction of horizontal cross braces on the middle tower column: The tower column has a teardrop-shaped structure. In order to reduce the adverse effects of excessive cantilever on the tower column during construction, it is planned to set three horizontal cross braces on the middle tower column. The elevations of the three horizontal cross braces are: +57.968m, +83.871m, and +118.353m respectively.

[0060] The horizontal brace of the tower column is made of Φ1200×14mm steel pipe and connected horizontally with the embedded parts of the tower column. Each active cross brace can achieve active top-to-top in order to adjust the line shape of the tower limb. The specific value of the top-to-top force shall be subject to the construction monitoring instructions. The embedded parts of the cross brace shall be made of galvanized steel plates, embedded before the concrete construction of the corresponding segment, and the corresponding segment cross brace shall be installed after the climbing formwork is climbed.

[0061] When the lower climbing frame of the climbing formwork is out of the horizontal brace position, the horizontal brace is constructed immediately. The third horizontal brace is constructed after the climbing formwork completes the 24th section. The tower column can be constructed upwards only after the horizontal brace is completed and the tower column line shape is adjusted according to the monitoring instructions.

[0062] Prestressed construction: 12Φs15.2 circumferential prestressed steel strands are set in the anchorage area of ​​the 13# to 16# steel anchor beam inclined cables to improve the crack resistance of the tower column. The circumferential prestressing adopts deep-buried anchors and tensioning technology at both ends. Steel bundle tensioning can only be carried out when the concrete strength and elastic modulus reach 90% of the design strength. Prestressed tensioning adopts an intelligent tensioning system, and grouting adopts a vacuum-assisted grouting process. After the pre-tensioning preparation work, the anchor and intelligent tensioning equipment are installed, and then prestressed tensioning, end sealing, prestressed grouting and anchor sealing are carried out. After the anchor sealing concrete is demoulded, it should be immediately watered and cured to strengthen the connection between the anchor sealing concrete and the tower concrete.

[0063] Steel anchor beam construction: The cable anchor structure uses steel anchor beams, which are set in the upper tower column to bear the balanced horizontal force of the cable. There are 16 types of steel anchor beams, divided into 4 categories, each anchoring a pair of cable stays. The steel anchor beams are composed of tension anchor beams and anchor structures. Each tower limb has 16 sets of steel anchor beam systems, numbered 1# to 16# from bottom to top, and are symmetrically arranged on both sides of the transverse center line of the main tower. The steel anchor beams are all supported on steel brackets.

[0064] After the steel anchor beam and steel bracket are installed as a whole, loosen the connecting bolts on one side before tensioning the cable. After tensioning, loosen the bolts on the other side to ensure that there is no constraint between the steel anchor beam and the steel bracket along the bridge. Use bolts with round holes at the ends. Insert the split pin after installation to prevent the nut from falling off. The nut should be on top when installing the bolts.

[0065] The steel anchor beam system is manufactured in sections in the factory, and the section components are assembled into a whole. Temporary connection matching parts are set between the corbel walls of each section of the steel anchor beam, and pre-assembled in the factory to check the manufacturing and assembly accuracy of the steel anchor beam system. After the steel anchor beam and steel corbel parts are transported to the construction site, they are temporarily stored on the construction platform.

[0066] The steel anchor beam and corbel are hoisted as a whole, and the steel corbel is connected as a whole through temporary connecting supports set at the upper and lower ends of the wall panel. After hoisting into place, the designed positions of the anchor beam and corbel are remeasured to complete the installation of the steel anchor beam system.

[0067] Before the construction of each section of the upper tower column, the steel anchor beam system is installed first, using a tower crane for installation. Except for the 1# steel anchor beam cable guide which is installed in advance, the remaining steel anchor beam cable guides are connected to the corresponding steel anchor beams as a whole and hoisted together.

[0068] After the steel anchor beam system is positioned, the segment reinforcement is tied, the formwork is installed, the concrete is poured, and the prestressing is tensioned according to conventional processes.

[0069] The 1# steel anchor beam is cast in the formwork when the 19th section of the tower column is under construction. The first section of the steel anchor beam system is precisely positioned using the bracket of the connector embedded in the top of the concrete during the construction of the 18th section. The 2# to 16# steel anchor beams are positioned in turn according to the position of the next steel anchor beam installed. If a large deviation in accuracy is found during the installation process, it needs to be adjusted in time.

[0070] The construction steps of steel anchor beam are as follows.

[0071] Step 1: Install the rigid frame on the poured concrete.

[0072] Step 2: Use a tower crane to hoist the steel anchor beam and steel corbel as a whole; hoist the steel anchor beam onto the rigid frame, use the steel anchor beam on the bottom layer for positioning, and use jacks and hand winches for precise adjustment; after the installation accuracy meets the specification requirements, connect and reinforce the steel corbel and the rigid frame.

[0073] Step 3: Tie up the steel bars, install the formwork and pour the concrete; after the concrete pouring is completed, remove the connecting bolts between the steel bracket and the steel anchor beam at one end to make it free; repeat steps 1 to 3 to install the remaining steel anchor beams.

[0074] Installation process of steel anchor beam system: The installation of steel anchor beam on the upper tower column is divided into two parts: first section installation and height connection installation. The first section installation needs to focus on pre-controlling the elevation, plane position and relative height difference between the wall panels.

[0075] 1) Construction of the first section of steel anchor beam:

[0076] Due to the shrinkage creep of the tower column concrete structure itself, as well as the compression deformation under the pressure of the cable axis, when constructing the steel anchor beam and concrete joint of the tower column, it is necessary to adjust the base elevation of the steel anchor beam system and set an appropriate pre-lift value. This value should be dynamically monitored during construction to ensure the accuracy of the cable anchor position on the tower. Specifically including.

[0077] ①Installation and erection of support frame.

[0078] In order to facilitate the accurate installation and adjustment of the plane position and elevation of the steel anchor beam, when constructing the concrete of the 18th section, the foundation embedded parts of the installation support steel bracket of the first section of the steel anchor beam are embedded in the top surface of the inner cavity of the upper tower column, and then the support bracket is installed and erected.

[0079] The bracket is welded with [16 channel steel, and the bottom of the bracket is supported on the embedded parts of the foundation. After the installation is completed, the top surface is ensured to be flat, and the flatness is controlled within 5mm. Before the steel anchor beam is dropped, the elevation of the top of the bracket is re-measured. According to the bottom elevation of the first section of the steel anchor beam to be installed, the bracket is padded, and the elevation is controlled by adding or reducing thin steel plates. If there is a deviation in the plane position when the steel anchor beam is dropped on the bracket, the plane position needs to be calibrated by a jack. After the plane position verification is completed, the elevation is calibrated by a thin steel plate prepared in advance. When the absolute elevation of the steel anchor beam meets the requirements, the steel anchor beam is temporarily fixed. In order to avoid the relative height difference of the four corners of the steel anchor beam wall panel exceeding the limit and affecting the subsequent steel anchor beam installation accuracy, it is necessary to observe the measurement results for two consecutive days and nights. When the final data is stable and meets the design requirements, the steel bracket wall panel is welded and fixed to the pre-installed rigid frame to complete the precise positioning of the first section of the steel anchor beam system.

[0080] ②Reinforcement of steel anchor beam corbel wall panels.

[0081] The bottom wall plate of the first section of the steel anchor beam corbel is 40mm thick. Before installation, a layer of contact support is set on the top of the corbel to prevent the corbel from deformation during the hoisting process. The contact support and the corbel are connected by bolts. The steel anchor beam system is hoisted with a special hanger to eliminate the internal force and deformation of the corbel wall plate.

[0082] ③Installation of cable guide tube and limit device.

[0083] The cable guide tube and the steel anchor beam are temporarily connected and hoisted together. According to the drawings, the upper and lower port coordinates of the intersection of the embedded cable guide tube and the inner and outer walls of the tower column are set out to control the installation axis to fit with the theoretical axis.

[0084] The cable duct positioning bracket is welded and set on the rigid frame installed in advance along the coordinate control points of the upper and lower ports of the cable duct. A positioning bracket is welded at each end of the cable duct, and an additional positioning bracket is added every 1m in the middle of the cable duct (at least one additional bracket is added).

[0085] The installation of the embedded cable guide tube is carried out after the steel anchor beam system is installed and positioned. At this time, the coordinates of the control points of the cable guide tube and the inner wall of the tower column (marked directly on the steel bracket with paint) have been determined (determined by the installation accuracy of the steel anchor beam). It is only necessary to re-measure the installation accuracy of the control point of the lower port of the steel sleeve (marked on the cross bar of the rigid skeleton). If the accuracy requirement of 5mm is not met, the position of the lower port is fine-tuned to a deviation of less than 5mm on the premise of meeting the smoothness requirement (at this time, the connecting bolts between the steel anchor beam and the steel bracket do not need to be tightened in place, and a gap is left for adjustment).

[0086] After the steel anchor beam is positioned, a longitudinal limit device of the steel anchor beam is installed. The limit device is perpendicular to the center line of the bridge tower. The limit device is connected and fixed by a pre-embedded steel plate pre-embedded in the tower wall. One end is welded to the upper end of the steel anchor beam, and the end of the limit device is melted through the steel anchor beam, and the other end is fixed on the pre-embedded steel plate.

[0087] 2) Standard section steel anchor beam construction:

[0088] After the first section of steel anchor beam is installed, the subsequent installations will be the standard section steel anchor beam system.

[0089] The hoisting method of the standard segment steel anchor beam system is the same as that of the first segment steel anchor beam system, and the bracket is hoisted together with the anchor beam. A butt bracket device (connector) is set on the inner side of the tower column on the steel anchor beam bracket wall plate to facilitate the smooth positioning of the heightening steel anchor beam. Two are set up on each side wall plate. The subsequent heightening installation is based on the butt bracket welded on the steel bracket wall plate installed last time for butt connection.

[0090] The butt brackets are connected by bolts and pins to avoid deformation of the wall panels caused by welding. At the same time, to ensure the installation accuracy of the wall panels, the butt brackets are machined in the manufacturer. The installation of the cable guide and the limit device in the standard segment steel anchor beam system is similar to the method in the first section steel anchor beam.

[0091] The installation of the steel anchor beam system is exactly the same as the pre-assembly method. First, install the two temporarily connected steel anchor beam brackets. When the bottom height of the hoisted steel bracket wall panel is about 20cm away from the steel bracket wall panel to be installed, slowly and carefully drop the height-connected steel anchor beam bracket. Personnel are on duty around the steel bracket to prevent the steel bracket to be installed from bumping against the installed steel bracket wall panel and the docking bracket. When the height and position of the height-connected steel bracket are basically aligned with the wall panel of the steel bracket installed in place last time, slowly release the tower crane hook until the weight of the steel bracket to be installed is all borne by the wall panel of the installed steel bracket. During this period, the position of the docking bracket should be fine-tuned to achieve the purpose of installing the connecting pin first and then the connecting bolt. At the same time, re-measure the top plane position, elevation and relative height difference of the four corners of the height-connected steel bracket. After all are qualified, the steel anchor beam is positioned. Re-measure the plane position, elevation and relative height difference of the top of the installed steel anchor beam. After all are qualified, tighten the bracket joint bolts to complete the installation of the standard segment steel anchor beam system. Then turn to the reinforced formwork concrete construction of the tower column of this segment. Repeat the cycle in sequence until the installation of all steel anchor beam systems is completed.

[0092] 3) Steel anchor beam installation measurement control:

[0093] The plane position, inclination and size inspection of the steel anchor beam are the same as those in the pre-assembly stage. In the continuous installation stage, the focus is on controlling the cumulative height difference of the wall panel (anchor point).

[0094] After the first section of the combined structure is positioned, the elevation benchmark previously measured by the total station zenith distance measurement method is transferred to the top of the first section of the steel anchor beam using a level and an identification steel ruler and marked. After each section is constructed, the elevation benchmark of the previous section is measured to the top of the steel anchor beam of this section using an identification steel ruler. In order to eliminate the error accumulation of elevation transfer, the elevation benchmark is checked and adjusted by the total station zenith distance measurement method every five sections of steel anchor beams.

[0095] In addition to temperature and wind correction and accurate positioning of the first section of the steel anchor beam, the following accuracy control measures should be taken for the installation of the steel anchor beam:

[0096] ① Accurately calculate the installation position of the first section of steel anchor beam.

[0097] Before installing the first section of steel anchor beam, the cable tower is monitored and the accurate plane position of the first section of steel anchor beam is determined through control analysis. At the same time, the pre-elevation value of the first section of steel anchor beam is calculated and determined.

[0098] The ideal target geometry of the steel anchor beam is given by the center point of the steel anchor beam section. The center line of the steel anchor beam overlaps with the center line of the upper tower column concrete section.

[0099] The Z value of the ideal target value is the design elevation superimposed with the following correction value (pre-elevation value): compensation for the compression of the middle and lower tower columns when the bridge is completed; the superelevation value used when the first section of the steel anchor beam is installed; compensation for the overlength of the steel anchor beam when the bridge is completed; foundation settlement; and compression of the steel anchor beam during the construction phase.

[0100] ② Adopt reasonable measurement methods to improve the measurement accuracy of steel anchor beam installation.

[0101] The installation and positioning of the main tower steel anchor beam and cable duct is the most difficult and requires the highest precision in measurement and control. The position of the cable duct has been accurately determined according to the relative geometric position when the steel anchor beam is manufactured. Accurate positioning of the steel anchor beam is essentially accurate positioning of the cable duct.

[0102] The installation and positioning of the steel anchor beam adopts the three-dimensional coordinate method of the total station, and the bottom elevation, top elevation and flatness of the steel anchor beam and steel bracket are measured by a precision level. The steel bracket and the steel anchor beam are hoisted as a whole. The steel bracket directly affects the installation accuracy of the first section of the steel anchor beam. Therefore, the accurate installation of the embedded base is the prerequisite for the accurate installation of the first section of the steel anchor beam.

[0103] The first step in the positioning measurement of steel anchor beams is to eliminate various external interferences, ensure that the cable tower is in a freely extended arm state, and select the early morning or evening for layout and positioning to eliminate the influence of the external environment on the measurement results as much as possible. If necessary, corrections can be made to improve the accuracy of measurement control.

[0104] ③Steel anchor beams are installed with steel pads for deviation correction.

[0105] Due to the deviation of the inclination of the steel anchor beam during manufacturing and installation, as the anchor beam is continuously connected, the pre-deviation gradually accumulates and increases, and the cumulative deviation of the anchor beam installation must be controlled. When the anchor beam is installed to a certain height, it is necessary to correct the deviation. If the elevation is lower than the design elevation during correction, a steel gasket is used to plug the gasket, that is, according to the batches of on-site anchor beams and hoisting, a layer of correction pads is set in each batch, and it is set at the position of the corbel where the steel anchor beams are grouped. When the steel anchor beam is manufactured, the height of the steel anchor beam on the upper side of each gasket is reduced accordingly, so that the sum of the gasket thickness and the height of the steel anchor beam after reduction is equal to the original design steel anchor beam height. If the elevation is higher than the design elevation, fine cutting is performed on the top of the wall panel to reduce the elevation.

[0106] Before a batch of anchor beams are installed and positioned, the actual inclination of the anchor beams is measured, and the adjustment value is determined based on the measured value. The pads are cut and installed together with the next batch of steel anchor beams.

[0107] Step 4: Construction of lower beam.

[0108] The top elevation of the lower beam is 29.468m, the top edge of the lower beam is horizontal, the arc radius of the bottom edge is 4718.9cm, and it adopts a variable-section box section. It is a prestressed concrete structure. The width of the lower beam is 6.5m and the wall thickness is 1.0m.

[0109] The lower crossbeam was constructed simultaneously with the 6th to 7th sections of the lower tower column at the same height, and the concrete pouring of the lower crossbeam was completed in two times. The first floor was completed simultaneously with the 6th section of the tower column, and the second floor was completed simultaneously with the 7th section of the tower column.

[0110] The lower cross beam is constructed with floor-standing steel pipe brackets. Bracket columns and flat joints are set up on the lower tower column connection plate, and the main beam and arc truss are installed. The arc truss is processed and formed in pieces at the processing plant and then transported to the construction site for piecewise hoisting. The truss is connected into a whole with steel sections in the longitudinal direction of the bridge, and finally the bottom formwork system is installed. After the bottom formwork of the lower cross beam is constructed, the bracket is pre-pressed. After the pre-pressing is completed, the steel bars are tied, the prestressed pipes are positioned, and the formwork is installed. Finally, the concrete is poured. The first pouring is 5.97m, and the second pouring is 2.5m.

[0111] Step 5: Construction of upper beam.

[0112] The top elevation of the upper beam is 92.0m, the arc radius of the top edge of the upper beam is 3337.2cm, and the arc radius of the bottom edge of the upper beam is 7675.8cm. It adopts a variable cross-section box section and is a prestressed concrete structure. The upper beam is 4.5m wide and has a wall thickness of 1.0m.

[0113] The upper crossbeam and tower column are constructed asynchronously. When the tower column is constructed to the 18th section, the upper crossbeam reinforcement is embedded. When the tower column is constructed to the 20th section, the upper crossbeam is constructed and cast in one step.

[0114] The upper crossbeam is constructed with corbel brackets. Corbel embedded parts are pre-embedded in the 17th section of the middle tower column, and the upper crossbeam bracket is set up on the corbel.

[0115] After the bottom formwork of the upper beam bracket is constructed, the bracket is pre-pressed. After the pre-pressing is completed, the steel bars are tied, the prestressed pipes are positioned, the formwork is installed, and finally the concrete is poured.

[0116] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A construction process for a main structure of a small-curvature teardrop-shaped cable tower, characterized in that: The following steps are involved: Step 1: Tower base construction; Step 2: Connection plate construction; Step 3: Tower column construction; Step 4: Construction of lower beam; Step 5: Construction of upper beam; Wherein step 2 comprises the construction of steel anchor beam, the integral hoisting of steel anchor beam and corbel, the steel corbel is connected as a whole by temporary connecting braces arranged at the upper and lower ends of the wall plate, after hoisting into place, the design positions of anchor beam and corbel are re-measured, and the installation of steel anchor beam system is completed, and the installation of embedded cable guide tube is carried out after the steel anchor beam system is installed and positioned, at this time, the connecting bolts between steel anchor beam and steel corbel do not need to be tightened in place, and a gap is left for adjustment, if the accuracy requirement is not met, the position of the lower port is fine-tuned until the deviation meets the accuracy requirement under the premise of meeting the smoothness requirement, after the positioning of steel anchor beam is completed, the longitudinal limit device of steel anchor beam is installed, the limit device is perpendicular to the center line of the bridge tower, the limit device is connected and fixed by the embedded steel plate pre-embedded in the tower wall, one end is welded to the upper end of steel anchor beam, the end of the limit device is melted through the steel anchor beam, and the other end is fixed on the embedded steel plate; In step 3, the tower column is constructed by hydraulic climbing formwork, and both the inner and outer formworks are made of wooden beam glued formworks, including panels, shaped wood, wooden back ribs and steel main beams. The inner and outer formworks are adjusted in the vertical curved section of the tower column by inserting shaped wood between the panel and the wooden beam. The shaped wood is made of wooden strips, processed according to the linear shape of the tower column, and fixed to the panel and the wooden beam by wooden nails; the panel and the wooden back ribs are connected by wood screws, and the wooden back ribs are connected to the steel main beam by connecting claws. Tie rods are used between the inner and outer formworks to overcome the lateral pressure of concrete; The steps of constructing the steel anchor beam include: Step 1: Install the rigid frame on the poured concrete; Step 2: Use the tower crane to hoist the steel anchor beam and steel bracket as a whole; hoist the steel anchor beam onto the rigid frame, use the steel anchor beam on the bottom layer for positioning, and use the jack and hand winch for precise adjustment; after the installation accuracy meets the specification requirements, connect and reinforce the steel bracket and the rigid frame; Step 3: Tie the steel bars, install the formwork and pour the concrete; after the concrete pouring is completed, remove the connecting bolts between the steel bracket and the steel anchor beam at one end to make it free; repeat steps 1 to 3 to install the remaining steel anchor beams; The construction of the first section of steel anchor beam includes the installation of support frame, reinforcement of steel anchor beam corbel wall plate, and installation of cable guide tube and limit device. Before the installation of the first section of steel anchor beam, a layer of connecting brace is set on the top of the corbel. Bolts are used to connect the connecting brace and the corbel. The steel anchor beam system is hoisted with a special hanger to eliminate the internal force and deformation of the corbel wall plate. The installation and erection of the support frame includes: pre-embedding the foundation embedded parts of the installation support steel bracket of the first section of the steel anchor beam on the top surface of the inner cavity of the upper tower column, and then installing and erecting the support bracket; the bottom of the bracket is supported on the foundation embedded parts, and after the installation is completed, the top surface is ensured to be flat, and the flatness is controlled within 5mm. Before the steel anchor beam is dropped, the elevation of the top of the bracket is re-measured, and according to the elevation of the bottom of the first section of the steel anchor beam to be installed, the bracket is padded, and the elevation is controlled by adding or reducing thin steel plates; if there is a deviation in the plane position when the steel anchor beam is dropped on the bracket, the plane position needs to be calibrated by a jack. After the plane position verification is completed, the elevation is calibrated by a thin steel plate prepared in advance. When the absolute elevation of the steel anchor beam meets the requirements, the steel anchor beam is temporarily fixed; in order to avoid the relative height difference of the four corners of the steel anchor beam wall panel exceeding the limit and affecting the subsequent steel anchor beam installation accuracy, it is necessary to observe the measurement results for two consecutive days and nights. When the final data is stable and meets the design requirements, the steel bracket wall panel is welded and fixed to the pre-installed rigid frame to complete the precise positioning of the first section of the steel anchor beam system.

2. The construction process of the main structure of a small-curvature teardrop-shaped cable tower according to claim 1 is characterized by: The cable duct is temporarily connected to the steel anchor beam and hoisted together to control the fitting of the installation axis with the theoretical axis. The cable duct positioning bracket is welded and set on the rigid frame that has been installed in advance along the coordinate control points of the upper and lower ports of the cable duct. A positioning bracket is welded at each end of the cable duct, and another positioning bracket is added every 1m in the middle of the cable duct. The pre-buried cable duct is installed after the steel anchor beam system is installed and positioned.

3. The construction process of the main structure of a small-curvature teardrop-shaped cable tower according to claim 2 is characterized by: After the installation of the first section of steel anchor beam is completed, the subsequent installation is all standard section steel anchor beam system. The construction of standard section steel anchor beam includes: the bracket is hoisted together with the anchor beam, and the steel anchor beam bracket wall plate is set with a docking bracket device on the inner cavity side of the tower column, with 2 upper and lower brackets set on each side wall plate. The subsequent height connection installation is based on the docking bracket welded on the steel bracket wall plate installed last time for docking connection; first install the two temporarily connected steel anchor beam brackets, and when the height and position of the height connection steel bracket and the wall plate docking bracket of the steel bracket installed last time are basically aligned, slowly release the tower crane. Hook, until the weight of the steel corbel to be installed is all borne by the wall panel with the installed steel corbel. During this period, the position of the butt corbel should be slightly adjusted to achieve the purpose of installing the connecting pins first and then the connecting bolts. At the same time, remeasure the top plane position, elevation and relative height difference of the four corners of the connected steel corbel. After all are qualified, the steel anchor beam is positioned; remeasure the top plane position, elevation and relative height difference of the installed steel anchor beam. After all are qualified, tighten the corbel butt bolts to complete the height connection installation of the standard segment steel anchor beam system; then turn to the reinforced formwork concrete construction of the tower column of this segment.

4. A construction process for a main structure of a small-curvature teardrop-shaped cable tower according to any one of claims 1 to 3, characterized in that: The step 3 also includes: the rigid frame is processed in sections and frames, hoisted on site, and connected into a whole with steel sections. The rigid frame includes column trusses, horizontal cross bars, horizontal truss outer frames and diagonal bars. The vertical main reinforcement of the tower column is tied in sections and connected by rolled straight thread joints. The stirrups and horizontal steel bars are connected by binding joints or lap welding.

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